Stem Canker Disease Research Articles

Double-stranded RNAs targeting Sphaerulina musiva silence DCL but not CYP51 in vitro, and fail to confer resistance to canker in transgenic poplar

Host-induced gene silencing (HIGS) is a common method for engineering plant protection against pathogens, although success requires double-stranded (dsRNA) uptake mechanisms that may not be present in all fungi. We explored HIGS in transgenic poplar to study and control Sphaerulina musiva, the cause of Septoria stem canker disease. HIGS transgenic poplars expressing dsRNA that targeted either or both S. musiva CYP51 and DCL were developed and screened for resistance to stem canker disease in two greenhouse inoculation trials. While differences in resistance between transgenic lines and wild-type controls were not detected, there was a correlation between greenhouse-expressed disease resistance and transgene expression among HIGS lines targeting S. musiva DCL. To evaluate the likelihood that HIGS or spray-induced gene silencing might be effective under some conditions, concurrent with greenhouse screening we studied: 1) S. musiva’s capacity for uptake of environmental dsRNA; 2) effects of in vitro silencing of CYP51 and DCL on fungal growth and target transcript abundance; and 3) persistence of dsRNA in culture. Uptake of fluorescently tagged dsRNA was not detected with confocal imaging. In dsRNA-treated cultures, fungal growth inhibition was not detected, and RNA was rapidly degraded. Of the five target transcripts tested after dsRNA treatment, only DCL1 had reduced expression. Knockdown of DCL1 along with the enhanced resistance among high-expressing HIGS events targeting DCL suggests some HIGS may have been observed. Further determination of the factors limiting dsRNA uptake by S. musiva are needed to determine if HIGS can be an effective technology for limiting stem canker.

Stem canker disease of Phaseolus vulgaris caused by Paramyrothecium roridum in Iran

Stem canker disease of Phaseolus vulgaris caused by Paramyrothecium roridum in Iran

In Vivo Leaf Inoculation: An Alternative Method to Assess the Disease Resistance of Hybrid Clones in Poplar Breeding of Stem Canker Disease.

Stem canker diseases caused by the pathogen Cytospora chrysosperma (Pers.) Fr.) and Botryosphaeria dothidea (Moug. ex Fr.) Ces. & de Not. are the two major forest diseases in the poplar plantations in China, sometimes which can destroy all the poplar seedlings or severely damage mature poplar forests. Hybrid breeding is the most direct and efficient method of controlling and managing tree diseases. However, assessing disease resistance or selecting disease-resistance clones based on In vitro stem inoculation is inefficient, time-consuming, and expensive, limiting the development of hybrid breeding of poplar stem canker disease. In this study, we proposed an alternative method to assess disease resistance to stem canker pathogens through in vivo leaf inoculation. The test materials used in this method can be on 1-year-old poplar saplings or the annual branches of perennial poplars in the greenhouse or the field. The critical step of this alternative method is the selection of inoculating leaves: the 5-7th newly matured leaves might be the most suitable. The second critical step of the leaf inoculation method is to make wounds on plant leaves through needle pierces, providing sufficient lesions to measure disease severity. For the adequate number of leaves produced in the early stage of poplar breeding, this in vivo leaf inoculation contributes to the rapid, accurate, and large-scale screening of the disease-resistance poplar clones to stem canker pathogens. Moreover, this leaf inoculation method will also serve as an efficient method for screening pathotypes of stem canker disease pathogen C. chrysosperma, B.dothidea, or other poplar stem canker pathogens.

Improved YOLOv5m model based on Swin Transformer, K-means++, and Efficient Intersection over Union (EIoU) loss function for cocoa tree (Theobroma cacao) disease detection

The cocoa tree is prone to diverse diseases such as stem borer, stem canker, swollen shot, and root rot disease which impedes high yield. Early disease detection is a critical component of diverse management processes that are implemented throughout the life cycle of cocoa plants. Consequently, several studies on the application of detection techniques to recognize diseases have been proposed by several researchers. This study proposes the YOLOv5m network for cocoa tree disease detection. The development of cocoa disease detection systems will aid farmers in early identification prompt response, and efficient management of related cocoa tree diseases which will ultimately increase yield and sustainability. To improve the performance of the YOLOv5m network, a Swin Transformer (Swin-T) was added to the backbone network to improve cocoa tree disease detection accuracy. By obtaining global information, the K-means++ algorithm was added to modify the choice of initial clustering locations, and Efficient Intersection over Union Loss (EIoU) was used as a bounding box regression loss function to speed up the bounding box regression rate, resulting in higher precision of the YOLOv5m network. The experimental assessment outcome of this study showed that the proposed method YOLOv5m (Swin-T, K-means++, EIoU) achieved 96% precision, mAP of 92%, and recall of 94%. Compared to the original YOLOv5m, precision improved by 5%, mAP improved by 6%, and recall by 5%. Comparing the proposed method to the conventional YOLOv5m, the latter showed improved performance and better accuracy with a high detection speed and compactness. This improvement offers a useful and effective method for detecting diseases related to cocoa trees.

In vitro evaluation of fungicides against eucalyptus stem canker pathogens in Ethiopia

Field surveys of Eucalyptus camaldulensis diseases were conducted during 2019-20 and 2020-21 in Ethiopia. This species was the most commonly planted in the surveyed fields and exhibited stem canker diseases. Sampling was performed from diseased stems and branches displaying clear symptoms. Morphological and PCR assays of the ITS1 and ITS2 loci were conducted to identify the fungal pathogens. Lasiodiplodia theobromae and Didymella pinodella were identified as the fungal pathogens causing E. camaldulensis stem canker diseases. Four nationally licensed fungicides viz. Vitra (copper hydroxide), Ridomil Gold (metalaxyl-M + mancozeb), Liveshow (pyraclostrobin + epoxiconazole), and Sabozeb (mancozeb) were evaluated for their in vitro control efficacy against the identified fungi at different concentrations (500, 1000, 1500, and 2000 ppm). Vitra and Liveshow were found to be the most effective fungicides at 2000 ppm for the control and treatment of E. camaldulensis stem canker diseases. The identification of L. theobromae and D. pinodella as causal agents of E. camaldulensis is crucial for targeted disease management strategies. The evaluation of four fungicides at different concentrations provided valuable information for selecting the most effective treatment options for practical management practices of the diseases. This research serves as the first report on the management of Eucalyptus disease in Ethiopia, laying the foundation for future studies and contributing to the development of sustainable disease management practices. The findings of this research can guide policymakers, researchers, and agricultural practitioners in implementing targeted fungicide applications to mitigate the impact of stem canker on Eucalyptus plantations and improve their productivity.

Low Genetic Variation Contrasts With Variable Morphotypes in Neoscytalidium dimidiatum From the Philippines and Their Aggressiveness to Dragon Fruit Species

ABSTRACTNeoscytalidium dimidiatum is an asexual, opportunistic and necrotrophic pathogen that causes the devastating stem canker disease of dragon fruit species (Selenicereus spp.). Despite this, information about its intraspecific diversity remains lacking. Examination of the morphological variations of 40 N. dimidiatum isolates hosted by S. megalanthus, S. monacanthus and S. undatus from eight allopatric regions in the Philippines detected three distinct morphotypes. Sequencing of three partial gene markers (ITS, ACT and TUB2) of representative isolates revealed low intraspecific genetic diversity of the pathogen from the three hosts. Phylogenetic analysis of internal transcribed spacer (ITS) sequences of the isolates in this study and worldwide collections of the phytopathogen in the GenBank database infers similar founding populations and the possible specificity of the dragon fruit‐infecting N. dimidiatum. Pathogenicity and aggressiveness assay of the isolates on detached stems of dragon fruit did not detect host specificity to S. monacanthus and S. undatus. However, some isolates (i.g., MBDF0802A, MBDF0808B, MBDF0339A and MBDF0007A) significantly had shorter latent period to the stems of S. undatus than S. monacanthus. A higher aggressiveness component of lesion size development on S. undatus stems by isolates from S. monacanthus was recorded suggesting a possible directional selection of highly aggressive N. dimidiatum in this host. This is the first population study on the phenotypic traits and the genetic structure of N. dimidiatum. Valuable inputs for further study of the pathogen are provided, which may help inform the design of management options for stem canker disease of dragon fruit.

Current status of pistachio diseases in countries of the Mediterranean Basin

AbstractIn the Mediterranean Basin, the pistachio crop is considered an emerging nut crop due to the dependence of the European nut markets on international imports. Consequently, the extension and intensification of pistachio production to nontraditional growing areas has promoted both classic and emerging diseases of this nut tree, which are limiting factors in crop production. Due to the limited interest in pistachio crops, the aetiology and epidemiology of the main pistachio diseases are poorly studied. Thus, this review summarizes the state of pistachio disease research, with particular attention given to the Mediterranean area. The information reported here is based not only on the literature, but also the advancement of our research on pistachio diseases conducted in both Italy and Spain. We describe the main fungal diseases of the tree canopy in Mediterranean countries, such as Botryosphaeria panicle and shoot blight, Septoria leaf spot, and stem, branch and trunk canker diseases, followed by the main soilborne diseases. In addition, we review minor and/or sporadic fungal diseases originating in not only the Mediterranean, but also other pistachio‐producing countries. Another section is dedicated to other diseases caused by bacteria, phytoplasmas, viruses and nematodes. Finally, we summarize the main control strategies adopted in Mediterranean Basin countries against pistachio diseases.

Percentage And Intensity Of Stick Cancer (Phythotora Palmivora. Butler) On Cocoa Plants (Theobroma Cacao) And Its Influence On Dry Cocoa Bean Production (Kg)

This study aims to determine the intensity and percentage of P. palmivora stem canker disease and identify the types of disease that occur on cocoa plant stems (Theobroma cacao) as well as the influence of the intensity and incidence of stem canker on stem canker disease. production of cocoa beans (T. cacao). The method used in this research is the observation method, the procedure for determining the research location was carried out by means of purposive sampling. The results of the research showed that the sample plants that were attacked by stem cancer showed symptoms of attack such as brown, purplish red stems, no holes, wet skin texture and black spots like rot. The highest percentage of stem cancer attacks was on plantation 3 at 37.78% and the lowest percentage of stem cancer attacks was on plantation 1 at 11.11%. The highest intensity of stem cancer attacks was on plantation 3 at 17.33% and the lowest intensity of stem cancer attacks was on plantation 1 (maintained) with an attack percentage of 6.39%. The results of observations on cocoa plant stem samples found a type of disease belonging to the Phytophthora palmivora fungus group at research locations 1, 2 and 3.

First Report of Stem Canker Disease Caused by Neoscytalidium dimidiatum on Euphrates Poplar in Xinjiang, China.

Euphrates poplar (Populus euphratica Oliv.) constitutes about 61% of the global poplar population, thriving in arid regions of western China (Wu et al. 2023). It plays a crucial role in maintaining ecological balance, securing oasis agriculture, and driving socio-economic progress in the region. During a June 2023 investigation in the P. euphratica forest within the Hotan area of Xinjiang (37°20'21″N, 79°21'15″E), over 12% of the P. euphratica trees displayed branch withering symptoms. The affected trees exhibited cracked bark, trunk decay, darkened coloration, and an eventual black coal-smoke-like appearance. Fungal spores were notably present beneath peeling bark on trunks and main branches. The deep ulcers extended longitudinally into the cambium, leading to tree mortality. In some cases, lateral spread into the sapwood caused dark discoloration of vascular tissue. Twenty diseased branches from various locations were collected and 5-10 mm2 lesions were excised from the edges. These were then surface-disinfected with 75% ethanol for 30 s and 1% sodium hypochlorite for 2 min. After three rinses with sterile distilled water, excess moisture was removed using sterile filter paper, followed by incubating the samples on Potato Dextrose Agar (PDA) medium. Cultures were subsequently grown at 25 ± 1 ℃ under a 12-h photoperiod for three days, thus resulting in the isolation of 25 fungal strains with similar morphological characteristics. All strains displayed rapid colony growth (40 mm/d). On PDA medium, the mycelium initially presented as a white colony, transitioning to an olive-green to greyish color, finally turning dark-grey to black. Colonies generated mycelia that disintegrated into 0- to 1-septate, cylindrical to round, hyaline to brown arthroconidia, occurring singly or in arthric chains, averaging 8.9 ± 2.1 μm × 4.9 ± 1.3 μm, with a length/width ratio of 1.79. Based on morphological characteristics, the isolates were identified as Neoscytalidium dimidiatum (Penz.) Crous & Slippers (Crous et al. 2006). Molecular characterization involved amplifying the partial internal transcribed spacer (ITS) region and translation elongation factor 1-α (TEF1-α) and β-tubulin (TUB2) genes using ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999), and BT2a/BT2b primers (Glass and Donaldson 1995). Sequences, available in GenBank (ITS: PP033096, PP033097, PP033098; TUB2: PP032812, PP032813, PP032814; TEF1-α: PP032815, PP032816, PP032817), exhibited 99-100% identity with the epitype N. dimidiatum Arp2-D (ITS, MK813852; TUB2, MK816354; TEF1-α, MK816355). Phylogenetic analysis, employing maximum likelihood and Bayesian inference on concatenated ITS-TEF1-TUB, was constructed using IQ-Tree and MrBayes3.2.7, revealing isolates clustering within the N. dimidiatum clade. Three isolates (HY01, HY02, and HY05) from different collection points were chosen for pathogenic investigation. Pathogenicity testing on one-year-old healthy P. euphratica seedlings involved removing a 4-mm-diameter bark plug using a cork borer. A 3-day-cultured N. dimidiatum plug of the same size was inoculated, with a blank PDA as control. The wound was covered with moistened sterile absorbent cotton and finally sealed with parafilm for three days. Experiments were repeated thrice. Symptoms manifested by day 2 post-inoculation, resembling the original symptoms by day 7. In the control group, plants remained healthy. N. dimidiatum was exclusively re-isolated from lesions on inoculated stems, confirmed as N. dimidiatum through morphological characteristics and sequence analysis, aligning with Koch's hypothesis. To our knowledge, this is the first report of N. dimidiatum inducing stem canker on P. euphratica in China. This pathogen has been reported on many tree hosts including citrus (Alananbeh et al., 2020), common fig (Güney et al., 2022), dragon fruit (Salunkhe et al., 2023), and Almond (Nouri et al., 2018). Therefore our findings will serve as a warning for authorities to a potential threat in China's P. euphratica and other trees cultivation. Thus, further epidemiological studies are essential for devising effective management strategies.

Botryosphaeria dothidea causes stem canker of Idesia polycarpa in China

AbstractIdesia polycarpa is a woody oil plant with great development and application prospects. However, stem canker disease of I. polycarpa was frequently observed in Henan and Hubei provinces of China in 2020–2022. The seriousness of the disease caused a large number of trees deaths, which affected seedling production and fruit yield, restricting the development of the I. polycarpa industry. We performed isolation, purification and pathogenicity analysis of canker samples. Pathogenicity tests reproduced typical canker disease symptoms on detached branches of I. polycarpa. Based on morphological observations, conidial morphology and phylogenetic analysis of isolates with high similarity to the rDNA internal transcribed spacer (ITS), EF‐1α and TUB2 sequences screened in GenBank by BLAST, the pathogen of canker disease on I. polycarpa was identified as Botryosphaeria dothidea. This is the first report of B. dothidea as the pathogen of stem canker of I. polycarpa.

A new genus and species of Cryphonectriaceae causing stem cankers on plantation eucalypts in South Africa

AbstractFungi in the Cryphonectriaceae are important canker pathogens of woody shrubs and trees in the Melastomataceae and Myrtaceae (Myrtales). During 2021 disease surveys in KwaZulu‐Natal (South Africa) plantations, a serious stem canker disease was discovered on species of Eucalyptus and Corymbia. The cankers had structures on their surfaces typical of fungi in the Cryphonectriaceae. The aims of the study were to identify the fungus associated with the disease and to test its pathogenicity. Morphological characteristics of both sexual and asexual structures and phylogenetic analyses based on partial sequences of the conserved nuclear large subunit (LSU) ribosomal DNA, the internal transcribed spacer (ITS) regions including the 5.8S gene of the ribosomal DNA operon, and two β‐tubulin (BT1/BT2) regions were used for identification purposes. Phylogenetic analyses of the sequence data and morphological characteristics supported the establishment of a new genus in the Cryphonectriaceae, for which the name Xanthoporthe myrticola gen. et sp. nov. is provided. Pathogenicity trials showed that isolates were pathogenic on tested Eucalyptus grandis and hybrids as well as Corymbia henryi. The results suggest that this is an emerging pathogen that could influence the sustainability of plantation forestry in South Africa.

Secreted Effector Proteins of Poplar Leaf Spot and Stem Canker Pathogen Sphaerulina musiva Manipulate Plant Immunity and Contribute to Virulence in Diverse Ways.

Fungal effectors play critical roles in manipulating plant immune responses and promoting colonization. Sphaerulina musiva is a heterothallic ascomycete fungus that causes Septoria leaf spot and stem canker disease in poplar (Populus spp.) plantations. This disease can result in premature defoliation, branch and stem breakage, increased mortality, and plantation failure. However, little is known about the interaction between S. musiva and poplar. Previous work predicted 142 candidate secreted effector proteins in S. musiva (SmCSEPs), 19 of which were selected for further functional characterization in this study. SmCSEP3 induced plant cell death in Nicotiana benthamiana, while 8 out of 19 tested SmCSEPs suppressed cell death. The signal peptides of these eight SmCSEPs exhibited secretory activity in a yeast signal sequence trap assay. Confocal microscopy revealed that four of these eight SmCSEPs target both the cytoplasm and the nucleus, whereas four predominantly localize to discrete punctate structures. Pathogen challenge assays in N. benthamiana demonstrated that the transient expression of six SmCSEPs promoted Fusarium proliferatum infection. The expression of these six SmCSEP genes were induced during infection. SmCSEP2, SmCSEP13, and SmCSEP25 suppressed chitin-triggered reactive oxygen species burst and callose deposition in N. benthamiana. The candidate secreted effector proteins of S. musiva target multiple compartments in the plant cell and modulate different pattern-triggered immunity pathways. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2023.

Evaluation of Fungicides as Protective and Curative Treatments against Canker Disease of Eucalyptus urograndis Caused by Chrysoporthe deuterocubensis in Malaysia

Over the years, Eucalyptus plantations have rapidly expanded in Sarawak, Malaysia, accounting for 19% of the total forest plantation area. In a routine forest health surveillance conducted in 2022 at Sarawak, Malaysia, tree stands of Eucalyptus urograndis (Eucalyptus grandis × Eucalyptus urophylla hybrid) were detected with symptoms of stem canker disease caused by Chrysoporthe infection. Given the limited information on the chemical control of Chrysoporthe stem canker disease, there is a growing need to develop effective chemical control strategies to protect and cure Chrysoporthe infection on E. urograndis trees. Therefore, this study aimed to identify the causal pathogen of this stem canker disease in 7-year-old E. urograndis trees in Sarawak, Malaysia, and evaluate the efficacy of various fungicides as curative or protectant treatments on canker infection using artificial inoculation methods. Fungal isolates were first collected and subjected to molecular identification and pathogenicity analysis. Then, in vitro efficacy tests were evaluated using five licensed fungicides: thiram, prochloraz manganese chloride, copper hydroxide, dimethomorph, and mancozeb. Subsequently, the performance of these fungicides was assessed through preventive and curative field experiments on 10-year-old E. urograndis trees using the artificial inoculation technique. Based on the morphological and phylogenetic analysis of the ITS1/ITS4, β-tubulin 2 (BT2), and the combined ITS1/ITS4 and BT2 sequences extracted from 20 fungal isolates, Chrysoporthe deuterocubensis was identified as the causal pathogen of the canker disease, with isolate CHRY18 recording the highest virulence. The in vitro efficacy tests showed that prochloraz manganese chloride achieved 100% inhibition against C. deuterocubensis at 1.0 mg/mL. In the preventive experiment, thiram significantly inhibited C. deuterocubensis infection, yielding the shortest lesion length (19.40 mm) compared to the non-treated control (47.48 mm) at 20 weeks post-inoculation. In the curative experiment, a significant reduction of 54.7% in lesion length was observed in inoculated symptomatic trees after 20 weeks of post-fungicide treatment with copper hydroxide. In conclusion, this study demonstrated prochloraz manganese chloride, thiram, and copper hydroxide as effective chemical controls of C. deuterocubensis stem canker on E. urograndis.

Location and timing govern tripartite interactions of fungal phytopathogens and host in the stem canker species complex

BackgroundLeptosphaeria maculans “brassicae” (Lmb) and Leptosphaeria biglobosa “brassicae” (Lbb) make up a species complex involved in the stem canker (blackleg) disease of rapeseed (Brassica napus). They coinfect rapeseed together, from the early stage of infection on leaves to the final necrotic stage at the stem base, and both perform sexual crossings on plant residues. L. biglobosa is suggested to be a potential biocontrol agent against Lmb, but there has been no mechanistic investigation of the different types of interactions that may occur between the plant and the two fungal species.ResultsWe investigated the bi- or tripartite interaction mechanisms by (i) confronting Lmb and Lbb in culture conditions or during cotyledon infection, with different timing and/or spore concentration regimes, (ii) performing RNA-Seq experiments in vitro or on the kinetics of infection of cotyledons infected by Lmb and/or Lbb to evaluate the transcriptomic activity and the plant response when both fungal species are inoculated together. Lbb infection of B. napus cotyledons was typical of a necrotrophic behavior, with a very early setup of one pathogenicity program and very limited colonization of tissues. This contrasted with the complex succession of pathogenicity programs of the hemibiotroph Lmb. During simultaneous co-infection by both species, Lmb was strongly impacted in its growth and transcriptomic dynamics both in vitro and in planta, while Lbb was unaffected by the presence of Lmb. However, the drastic inhibition of Lmb growth by Lbb was ineffective in the case of delayed inoculation with Lbb or a lower amount of spores of Lbb compared to Lmb.ConclusionsOur data suggest that Lmb growth inhibition by Lbb is the result of a combination of factors that may include competition for trophic resources, the generation by Lbb of an environment unsuitable for the lifecycle of Lmb or/and the effect on Lmb of plant defense responses induced by Lbb. It indicates that growth inhibition occurs in very specific conditions (i.e., co-inoculation at the same place of an equal amount of inoculum) that are unlikely to occur in the field where their coexistence does not prevent any species from completing their life cycle.

Biological control potential of a soil fungus Trichoderma asperellum K1-02 against Neoscytalidium dimidiatum causing stem canker of dragon fruit

Stem canker on dragon fruit caused by the fungus Neoscytalidium dimidiatum negatively impact dragon fruit cultivation and production. The use of Trichoderma species, the biological control agent against stem canker disease is an alternative way instead of use of synthetic fungicides. This study aimed to test the antifungal activities of soil fungi Trichoderma against N. dimidiatum. Ten isolates of Trichoderma species were tested against N. dimidiatum via dual culture assay, and the results showed that percentages of inhibition ranged from 72.75 to 84.45%. Trichoderma species K1-02 was found to be the most effective strain against N. dimidiatum (84.45%). Trichoderma K1-02 was identified based on a morphology and molecular study of internal transcribed spacer (ITS), the second largest subunit of RNA polymerase II (rbp2), and the translation elongation factor 1-alpha (tef1-α) as Trichoderma asperellum K1-02. The pre-colonized plate method demonstrated that T. asperellum K1-02 covered the tested plates at a rate of 60%, which was significantly higher than N. dimidiatum (40%), and T. asperellum K1-02 aggressively covered the mycelia of N. dimidiatum as observed via stereomicroscopy. An enzyme assay was conducted to test the activities of cell wall-degrading enzymes (CWDEs) in cell-free culture filtrate (CF) released by T. asperellum K1-02, and the results showed that the activities of chitinase and β-1,3-glucanase were significantly higher than those of the control (potato dextrose broth alone). Scanning electron microscopy of N. dimidiatum mycelia incubated with cell free CF of T. asperellum K1-02 showed abnormal morphology. Furthermore, an in vivo test was conducted on dragon fruit cladodes to test the ability of Trichoderma with respect to the reduction of canker lesions. The results revealed that the application of 106 spore/mL T. asperellum K1-02 spore suspension suppressed disease development via the reduction of canker areas (0.09 cm2) on dragon fruit cladodes at a significantly higher level than those inoculated by pathogens alone (0.49 cm2). Thus, T. asperellum K1-02 demonstrated antifungal abilities against N. dimidiatum and has the potential to control stem canker on dragon fruit.

Characterisation of Chrysoporthe cubensis and Chrysoporthe deuterocubensis, the Stem Canker Diseases of Eucalyptus spp. in a Forest Plantation in Malaysia

Commercial plantations of Eucalyptus species have been established in Malaysia, especially during the past 10 years, with the aim of sustaining the supply of wood and timber products for industrial use in Malaysia. As part of an assessment of fungal diseases affecting Eucalyptus species in four regions in Malaysia, including Kelantan, Pahang, Sabah, and Selangor, stem canker disease was discovered to be a widespread disease infecting Eucalyptus species in Malaysia. This study aimed to identify the fungus-causing stem canker disease, test its pathogenicity in Eucalyptus, and determine the mating type of isolates from the infected trees. The fungi were identified based on morphology and through comparisons of DNA sequence data from the ITS, β-tubulin 2 gene, and TEF-1α gene regions. Phylogenetic analyses showed that the causal agent of the stem canker was Chrysoporthe cubensis infecting Eucalyptus plantations in Pahang and Chrysoporthe deuterocubensis infecting Eucalyptus plantations in Kelantan, Sabah, and Selangor. We believe this is the first report of Chrysoporthe cubensis-infected Eucalyptus in Malaysia and Southeast Asia, while Chrysoporthe deuterocubensis is the first-reported species infecting Eucalyptus pellita in Malaysia. Moreover, the fact that the mating-type MAT1-1 and MAT1-2 genes and the pheromone genes ppg1, ppg2, pre1, and pre2 were identified in all isolates indicates that Chrysoporthe cubensis and Chrysoporthe deuterocubensis are homothallic mating systems. Pathogenicity was tested on a 3-year-old standing tree, 1-year-old seedling, and detached healthy leaves, which were re-isolated for fulfilling Koch’s postulates. In pathogenicity trials, both Chrysoporthe cubensis and Chrysoporthe deuterocubensis gave rise to lesions on wounded Eucalyptus. Both Chrysoporthe spp. were equally pathogenic to Eucalyptus urograndis and Eucalyptus pellita and should be regarded as a biosecurity concern in Malaysia’s forest plantation industry.

Statement of Retraction: In vitro assessment of fungicides efficacy against fungal isolates causing eucalyptus stem canker diseases in Ethiopia

Statement of Retraction: In vitro assessment of fungicides efficacy against fungal isolates causing eucalyptus stem canker diseases in Ethiopia

Characterization and report of Ectophoma multirostrata, causing stem canker disease in highbush blueberry in Iran

AbstractDuring a disease survey in greenhouses of blueberry seedlings in Mohammad Shahr City, Alborz Province, Iran, in the autumn 2021, severe stem canker symptoms were observed in the cv. Emerald of highbush blueberry (Vaccinium corymbosum). The disease incidence in the affected greenhouses was more than 30%–40%. Diseased branches and stems were sampled and the associated fungus was isolated on potato dextrose agar. Based on the fungal morphological features of the colony, three isolates among which the representative isolate of UT2020 were identified as Ectophoma multirostrata. Phylogenetic analysis of the concatenated ITS‐rDNA and beta‐tubulin (tub2) gene sequence data confirmed the morphological identification of the fungal isolates. E. multirostrata differs from closely related species by having several ostiolar necks, textura angularis wall in pycnidia and oblong to ellipsoidal conidia. The pathogenicity of the isolate UT2020 in the stems of highbush blueberry cv. Emerald was confirmed by our artificial wound inoculation method. After 14 days, the same stem canker symptoms were developed on the inoculated stems, and the same fungal isolate was re‐isolated from the newly developed symptoms, fulfilling the Koch's postulates. This is the first report of E. multirostrata causing a stem canker disease in highbush blueberries. Also, Vaccinium corymbosum is reported as a new host (matrix nova) for E. multirostrata worldwide.

First Report of Stem Canker on Dangshen (Codonopsis pilosula) Caused by Binucleate Rhizoctonia AG-K in China.

Dangshen (Codonopsis pilosula) is a well-known medicinal and food homologous plant in China, which is widely used as a tonic agent and has good immunomodulatory effects (Bai et al. 2020; Luan et al. 2021). To retain the best medicinal properties, growers imitated the original ecological planting method for cultivating C. pilosula in hillside fields in Wutai county, Shanxi province, China. In July and August 2021 and 2022, stem canker disease was observed in C. pilosula. The basal part of the stems showed slightly sunken brown lesions, and the disease incidence was up to 20% in the investigated fields (6.67 ha). To identify the causal agents of stem canker, 12 small pieces (approximately 5 mm long) from 12 diseased samples (one piece per sample) were cut from the border of the lesions, surface-sterilized (70% ethanol for 30 s, 0.5% NaClO for 3 min), washed three times with sterile water, and then incubated on water agar (WA) at 25 °C for 24 h. Isolates with right-angle branching, a septum near the branch, and a slight constriction at the branch base were selected, and their hyphal tips were transferred onto potato dextrose agar (PDA) plates. After incubation at 25 °C, 12 Rhizoctonia-like isolates (Dcp-19 to Dcp-30) with white colonies were obtained. White monilioid cells in aerial mycelia formed as they aged but did not produce sclerotia. Based on nuclear fluorescence staining with 1 μg·mL-1 4'-6-diamidino-2-phenylindole as described by Ahvenniemi et al. (2009), there were two nuclei per hyphal cell for all the 12 isolates. Moreover, the sequences of internal transcribed spacer region of ribosomal DNA (rDNA-ITS) of all the 12 isolates were amplified using the primers ITS1/ITS4 (White et al. 1990). For identical sequences, only the rDNA-ITS sequence (674 bp) of Dcp-19 has been deposited in GenBank (accession no. ON004932) and BLASTn analyses showed 100% homology with Rhizoctonia AG-K (MF070696). Maximum likelihood phylogenetic analysis further confirmed the identification. Healthy C. pilosula plants grown for two years in hillside fields were transplanted into sterile soil for pathogenicity testing. And the 12 isolates were all done in this test. Sterilized wheat seeds were placed on a 2-day-old colony of the isolate and incubated for 7 days. One fungus-infested seed was placed at the base of the stem and covered with sterilized soil. Control plants were inoculated with sterilized wheat seeds. Tests were performed on three plants for each isolate. The experiment was repeated twice. All the plants were cultivated at 22 °C and 50% relative humidity. After three weeks, the basal stems of the control plants were still healthy and did not have lesions, but the treated plants exhibited sunken brown canker lesions. The mean disease incidence of all the 12 isolates was 58.33%. The AG-K isolates re-isolated from the lesions of treated plants were confirmed by the morphological and molecular characteristics mentioned above, fulfilling Koch's postulates. To our knowledge, this is the first report of stem canker on C. pilosula caused by binucleate Rhizoctonia AG-K in China.

In vitro bioefficacy of Trichoderma species against two Botryosphaeriaceae fungi causing Eucalyptus stem canker disease in Ethiopia

Phytopathogenic fungi, which are leading to significant economic and production losses, pose a serious threat to global forestry. Field surveys were carried out on Eucalyptus trees in Ethiopia between 2019/20 and 2020/21. The E. camaldulensis predominantly grew in the surveyed fields and was severely affected by progressive stem canker disease. The diseased stems and branches exhibiting symptoms were collected, and the Lasiodiplodia theobromae and Neofusicoccum parvum fungal pathogens were identified via morphological and DNA sequence analyses of ITS1 and ITS2 from rDNA. The objective of this research was to assess the in vitro growth inhibition potential of Trichoderma species against Lasiodiplodia theobromae and Neofusicoccum parvum fungal species. Researchers are now exploring alternate eco-friendly management strategies due to the hazardous effects chemical fungicides have on human and environmental health. The use of biocontrol agents, such as Trichoderma species, is one of the potential approaches employed today. The antagonistic activities of Trichoderma asperellum (T4), Trichoderma asperellum (T5), Trichoderma atroviride (T1), Trichoderma atroviride (T11), Trichoderma longibrachiatum (T3), and Trichoderma longibrachiatum (T31) were tested in vitro against Lasiodiplodia theobromae and Neofusicoccum parvum that cause canker disease symptoms in E. camaldulensis. In all antagonism tests, T. asperellum and T. longibrachiatum effectively inhibited the growth of L. theobromae and N. parvum. This implies that the Trichoderma species could be useful to control E. camaldulensis canker disease.